线性磁悬浮织针驱动系统运动控制与实验分析

Motion control and experimental analysis of linear maglevknitting needle actuator

为解决传统织针驱动系统性能不佳以及磁阻式磁悬浮织针驱动系统的电磁力非线性问题,提出一种线性的洛伦兹力磁悬浮织针驱动系统。基于已有驱动系统实验平台,首先对系统的电磁力输出进行了测试,得出电磁力输出与线圈电流呈线性关系且与线圈所在磁场位置无关;其次设计了系统自适应鲁棒滑模控制器并进行实验,在该控制下织针0.6 s达到稳态且过程无超调量产生,系统具有较好的扰动抑制能力,且稳态误差保持在±15μm之间;最后将自适应鲁棒滑模控制与比例积分微分(PID)闭环反馈控制的实验结果进行对比分析。实验结果表明,洛伦兹力磁悬浮织针驱动系统为线性系统,且线性度较高,自适应鲁棒滑模控制系统具有较好的控制效果,且与PID控制相比在提高响应速度、控制超调量与抗干扰方面具有明显优势。

Objective Aiming at the poor performance of the traditional knitting needle drive system and the electromagnetic force nonlinearity of the reluctance force actuated maglev knitting needle drive system,a linear Lorentz force actuated maglev knitting needle drive system is proposed,and the adaptive robust sliding mode control is used to improve the system response speed,disturbance suppression ability,and robustness,realize the stable control of magnetic levitation knitting needles.Method An electromagnetic force testing system was built to measure the linear characteristics of the driving force through a single-DOF force sensor.The robust and adaptive aspects were taking into account in the differential equation of the system,and an adaptive robust sliding mode controller was designed to improve the system response speed,disturbance suppression ability and adaptability to system uncertainty.A prototype of the Lorentz force actuated maglev knitting needle drive system was built,and the performance of the maglev knitting needle drive system was verified through experiments.Results Twelve test points were evenly distributed within the effective stroke of the knitting needle to test the output characteristics of the electromagnetic force.Experiments showed that under the same current excitation condition,the output of electromagnetic force at each test point was consistent(Fig.4).At different test positions,the electromagnetic force varied linearly with the continuously changing excitation current(Fig.5).It showed that the driving force of the Lorentz force actuated knitting needle drive system had a linear relationship with the input current and had nothing to do with the output position.Under the action of adaptive robust sliding mode control,the step response of the system demonstrated that the knitting needle reached a steady state in 0.6 s without overshoot(Fig.7(a)),and the steady-state error remained within±15μm(Fig.7(b)).Compared with proportional,integral,and derivative(PID)control,adaptive robust sliding mode control had a faster response speed(Fig.9),but its steady-state noise was about 1.5 times that of PID control(Fig.10).It was found that the adaptive robust sliding mode control had a large static error due to the influence of chattering,while the PID control had a smaller static error of the knitting needle and better steady-state control performance.When the system was disturbed,the two control methods could restore the needle displacement to a steady state(Fig.11),but the system would have a displacement deviation of about 0.7%under the PID control,causing 20μm in a short time,while the displacement of the knitting needle did not change significantly under the adaptive robust sliding mode control.Compared with PID control,the disturbance suppression ability and robustness of the system was stronger under adaptive robust sliding mode control.The response of the′three-position knitting′excitation trajectory showed that the system could reach the height of looping,tucking,and floating line and make a stable stop,and the actual displacement was consistent with the expected displacement.Under the action of the adaptive robust sliding mode controller,the designed system was able to drive the knitting needle to complete the′three-position knitting′action.Conclusion The experimental results show that the Lorentz force actuated maglev knitting needle drive system is a linear system with high linearity.The designed adaptive robust sliding mode control system has a good control effect,and compared with PID control it has obvious advantages in improving response speed,reducing overshoot and disturbance rejection ability.The designed knitting needle drive system can complete the′three-position knitting′action.